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Thumbscrew (fastener)

Part of a series on
Screw drive types
Screw Head - Slotted.svg Slot
Screw Head - Phillips.svg Phillips
PH
Screw Head - Pozidrive.svg Pozidriv (SupaDriv)
PZ
Screw Head - Frearson.svg Frearson
Screw Head - Square External.svg Square
Screw Head - Robertson.svg Robertson
Screw Head - Hex External.svg Hex
Screw Head - 12-Point external.svg 12-point flange
Screw Head - Hex Socket.svg Hex socket (Allen)
Screw Head - Hex Socket Tamperproof.svg Security hex socket (pin-in-hex-socket)
Screw Head - Torx.svg Torx
T & TX
Screw Head - Torx Tamperproof.svg Security Torx
TR
Screw Head - TA.svg TA
Screw Head - Tri-wing.svg Tri-Wing
Screw Head - Torq-set.svg Torq-set
Screw Head - Spanner.svg Spanner head
(pig nose)
TH
Screw Head - Clutch Type G.svg Clutch
A & G
Screw Head - One-way Clutch.svg One-way
Screw Head - Double Square.svg Double-square
Screw Head - Triple Square.svg Triple-square
XZN
Screw Head - Polydrive.svg Polydrive
Screw Head - Spline.svg Spline drive
Screw Head - Double Hex.svg Double hex
Screw Head - Bristol.svg Bristol
Pentalobular.svg Pentalobe
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A screw drive is a system used to turn a screw. At a minimum, it is a set of shaped cavities and protrusions on the screw head that allows torque to be applied to it. Usually, it also involves a mating tool, such as a screwdriver, that is used to turn it. The following heads are categorized based on commonality, with some of the less-common drives being classified as "tamper-resistant".

Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00" or "Torx T5". These sizes do not necessarily describe a particular dimension of the drive shape, but are often arbitrary designations in the same sense as a "Size 8" dress.

The slot screw drive has a single slot in the fastener head and is driven by a "common blade" or flat-bladed screwdriver. It was the first type of screw drive to be developed, and for centuries it was the simplest and cheapest to make. The slotted screw is common in simple woodworking applications, but is not often seen in applications where a power tool would be used because a power driver tends to slip out of the head, potentially damaging the surrounding material. The tool used to drive a slot is called a common blade, standard, flat-blade, slot-head, flat-tip or flat-head/flathead screwdriver.

A cross or double-slot screw drive has two slots, oriented perpendicular to each other, in the fastener head; a slotted screwdriver is still used to drive just one of the slots. This type is usually found in cheaply-made roofing bolts and the like, where a thread of 5 mm (0.20 in) or above has a large flattened pan head. The sole advantage is that they provide some measure of redundancy: should one slot be deformed in service, the second may still be used.

The following are screw drives based on a cruciform shape; i.e., a cross shape. Other names for these types of drives are cross recessed, cross-head, cross tip, and cross-point. A double slotted screw drive is not considered cruciform because the shape is not recessed, and consists only of two superimposed simple milled slots.

The Phillips screw drive was created by John P. Thompson, who after failing to interest manufacturers, sold his design to businessman Henry F. Phillips. Phillips is credited with forming a company (Phillips Screw Company), improving the design, and promoting the adoption of his product. The original patent expired in 1966, but the Phillips Screw Company continued to develop improved designs.


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Wikipedia

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